The reference to only fearing "fear itself" at the beginning of To Kill a Mockingbird is an allusion to Franklin D. Roosevelt's inaugural speech.
The main similarity between both poems; the purple cow by Gellett Burgess and the mending wall of Robert Frost is their humorous language.
The American Poet Robert Frost explores the theme of humor in his poem "The Mending Wall". Just like the line, "Spring is the mischief in me, and I wonder if I could put a notion on his head."
Before 1789, the U.S. had been ruled by the Articles of Confederation (1781) in fear of govt. abusing power (like British rule). In 1787, it was obvious that they needed a perfect Union and so, while protecting the independence of states, the Articles of Confederation didn't describe the powers of a federal chief executive nor a judicial system. The creation of our Constitution and present form of government was informed by these and other considerations that arose during the years of the Confederation.